1. Field of the Invention
The present invention relates to an engine automatic stop and restart apparatus which automatically stops an engine when a predetermined engine automatic stop condition is satisfied, and restarts the engine when a restart condition is satisfied, thereafter.
2. Description of the Related Art
Conventionally, there is developed an engine automatic stop and restart system for the purpose of improving fuel consumption of an automobile and reducing environmental load, in which when a driver's operation satisfies a predetermined condition for stopping an engine (for example, a brake ON operation at a vehicle speed lower than a predetermined speed), fuel supply is automatically cut off so that the engine is automatically stopped, and after that, when a driver's operation satisfies a predetermined condition for restarting the engine (for example, a brake releasing operation, an accelerator depressing operation, and the like), fuel injection is restarted so that the engine is automatically restarted.
For instance, there is proposed an apparatus having the following structure (see, for example, Japanese Patent Application No. 2010-033545). When a request to restart is issued in a period when engine rotation is decreasing just after the idling stop, if it is judged that an rpm of the engine can be resumed by itself by restarting the fuel supply, the engine is restarted only by restoring the fuel supply without using a starter. In addition, when it is judged that the rpm of the engine cannot be resumed by itself by restarting the fuel supply, the fuel supply is restarted and the starter motor is rotated so that connection or disconnection between a ring gear and a pinion gear is performed based on the rpm of the engine, the rpm of the pinion gear, and a result of the judgment by the engine self-resumption judgment unit.
However, the conventional technology has the following problem.
FIG. 12 is an explanatory diagram of a restart operation in the conventional technology. In the case of the conventional apparatus described in Japanese Patent Application No. 2010-033545, the following operations are performed as illustrated in FIG. 12.
(1) When it is judged that the rpm of the engine cannot be resumed by itself by restarting the fuel supply after the engine stops by the idling stop, the fuel injection is performed simultaneously with a time t1 when the request to restart the engine is issued, and the starter motor is supplied with electricity so as to increase the rpm of the pinion gear, namely the rpm of the starter motor.
(2) Then, engagement between the ring gear and the pinion gear is started at a time t2 when an rpm difference between the rpm of the starter motor and the rpm of the engine becomes smaller than a predetermined rpm difference.
However, when an increase of the rpm of the engine occurs due to combustion of the engine at a time t3 before the engagement between the pinion gear and the ring gear is completed, the rpm deviation between the rpm of the pinion gear and the rpm of the engine is not decreased in the period until it is judged that the restart of the engine is completed at a time t4. Therefore, the pinion gear and the ring gear cannot engage with each other appropriately while having a relative rpm difference, and interfere with each other. Thus, there is a problem that noise (gear stripping sound) and gear abrasion are generated in the restart operation.